T-45 minutes and counting

I’ve now added all the features the ephemeral rig system needs to actually be used for animating a real shot, so that’s what I’ll be doing next. At 2287 lines, it is by far the largest programming project I have ever personally completed. Here’s a few words on those last, crucial features.

One obvious question that comes up about ephemeral rigging is how you zero things. Normally, you’d zero things by putting zeroes in every channel. (Except scale, or any other attribute that multiplies something else. We’ve all made that mistake at least once.)

For ephemeral rigging, this makes no sense. There is no “zeroed” space for anything to return to, except the actual center of the scene. Indeed, I intend to animate with an ephemeral rig while keeping the channel box entirely hidden! It serves no useful purpose in the interpolationless, ephemeral context.

But we can’t do away with the concept entirely. It will still be necessary to be able to return controls to some sort of “default” state. Without a meaningful parent space, the only kind of “default” that makes any sense is for ephemeral controls to be able to default to a specific relationship to each other.

Allow me to demonstrate.

To make this possible without parent spaces, I have each control store it’s default TRS values on the node as extra attributes. Because everything in the ephemeral rig is in the same space, pulling these values and building a matrix out of them is precisely the same as getting the world matrix of the node when it’s in its default position. I can therefore get those values at any time and find out where the node should be relative to any other node by comparing it’s default matrix to the default matrix of that node.


In this case, I’ve implemented zeroing through forward mode ie. zeroing a control will return it to it’s default relationship to its forward driver, and take it’s “child” controls with it. In theory there’s no particular reason that zeroing must be limited to the forward relationship. You could zero backwards, or sideways, or whatever you want. But figuring out how to make this accessible to the user in a clear way is tricky, so I’ve fallen back on the most basic functionality for the moment. I expect this will be the most common use of zeroing, in any case--while it’s completely essential to be able to zero out a control in some way, I don’t actually anticipate using it all that much.

It’s worth noting that in order to zero these controls, I actually have to build a whole ephemeral graph. Other controls may depend on them, and the controls being zeroed themselves must be zeroed in the correct order if they depend on each other. Because this is basically similar to the breakdown graph (ie. multiple controls can be used to start tracing the graph) I’ve made this a special case of the breakdown graph build.

Another new feature I’ve just added is “dummy” controls. These are temporary controls that allow you to pivot a control from any location, without actually adjusting the pivot of anything.

One thing I dislike about Maya’s transforms is the way pivot offsets get in between the ideally one-one relationship between its TRS values and its matrix. There’s a reason why we generally “buffer” a control instead of freezing transformations--adding an additional transform to cleanly change a node’s parent space is preferable to dealing with pivots.

That said, you obviously want to have pivot-like behavior, even if no actual pivots are used in the Maya transform sense. In the ephemeral rig system, this is actually rather easy to do--since there is already a concept of “pairing” nodes to allow for temporary connections between ephemeral controls, a “pivot” is simply an additional control that gets paired with whatever control you are using.

To keep with my philosophy that the ephemeral rig system never changes the topology of the Maya node graph (other then creating message connections that have no effect on the Maya scene) and does all ephemeral behavior internally, this control is not created or added as needed--it already exists in the scene, just hanging out waiting to be used. When you’re done using this “dummy” to pivot a control, it simply vanishes from view until needed again.

Finally, I’ve added a little HUD to the system that hovers around in the corner of the viewport, giving you an indication of which interaction mode in currently active. This allows me to shift changing the interaction mode back to hotkeys, which is much smoother then using the menu all the time (although I’ve left the options in the menu in case I ever need them there).

Like most of the GUI I have here, these are all represented by meshes in the scene. I know that using meshes to create GUIs is wrong, but I just can’t stop.